Hydrodynamics of gas stirred melts: Part I. Gas/liquid coupling
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I.
III.
INTRODUCTION
SUBMERGED gas injection into melts contained in furnaces, ladles, or similar transfer vessels has been commonplace since the days of Bessemer. Today's steelmaking examples include the bottom blown, side blown, and combination blown oxygen processes. In ladle metallurgy, desulfurization by submerged pneumatic injection of powders, pellets, and so forth into liquid iron or steel is popular. Parallel examples can be cited for the nonferrous industries. For instance, submerged gas injection plays an important role in copper and aluminum processing. Despite the ubiquitous nature of submerged gas injection, much remains to be done before these gas/liquid interactions can be described in a quantitative sense. Nevertheless, as fluid dynamics plays such a key role in determining the efficiencies of so many transport controlled metallurgical processes, such an objective is clearly worthwhile.
II.
PRESENT W O R K
The purpose of the present work is to analyze the way in which submerged gas jets interact with liquids to cause stirring. To demonstrate the approach, the problem has been set in its most simple form, i. e., the central injection of gas into a cylindrical vessel, the latter representing, to a first approximation, a ladle or furnace. In Part I a literature review is made and various authors' findings and proposals regarding submerged gas injection and gas stirred vessels are reconsidered. Following this, a fresh approach is taken to suggest how gas-liquid coupling can be tackled, and how a quantitative macroscopic model for liquid stirring can be built from first principles. In Part II, the implications and predictions of the macroscopic model are compared to equivalent but more detailed computations based on numerical solutions to the governing differential equations of continuity, motion, and turbulence. Again, previous work in this field is reconsidered. Y. SAHAI, Senior Research Associate, and R . I . L . GUTHRIE, Professor, are both with the Department of Mining and Metallurgical Engineering, McGill University, Montreal, Quebec, Canada H3A 2A7. Manuscript submitted June 26, 1981.
METALLURGICAL TRANSACTIONS B
PREVIOUS WORK
Gas Stirred Melts Since ladle injection metallurgy is becoming such an intrinsic part of steel processing operations, the theoretical and industrial aspects of these processes have naturally been considered at some length at a number of recent symposia. 1-4 Figures l(a), l(b), and l(c) have been taken from such publications5'6'7 to illustrate current ideas regarding hydrodynamics in these gas stirred systems. Figure l(a) shows, in schematic form, argon issuing from a porous plug at the bottom of a 150 tonne ladle of steel. 5 The diagram seems to suggest that very small spherical bubbles are released from the pores of the plug, and that following considerable expansion, they reach the bath surface. Figure 1(b) shows another idea of the hydrodynamic phenomena at play. 6 In this schematic, the bubble column is approximated to a vertical cylindrical column of spherical
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